Treatment of oil wells to prevent emulsification



Patented Nov. 10, 1942 UNITED STATES PATENT OFFICE murmur or on. WELLS'ro PREVENT EMULSIFICATION m Drawing. Application March 11, 19 41,

' Serial No. 382,781

The object of the invention is to eliminate, or

- to reduce to an important extent, the amount of emulsion produced inpumping oil wells which yield hard waters along with the oil.

It is well known that oil wells which produce alkaline waters along withthe oil are apt to yield an oil containing a highly refractory emulsion,which is dlflicult to resolve and separate after the oil has beenbrought to the surface. It is also known that the emulsions so formedare refractory because they are stabilized by salts of magnesium andcalcium with certain organic acids (e. g., naphthenic acids) which arecommonly present in the crude oil.

It has been proposed to introduce water softening agents into suchwells, to combine with the alkali earth metals of the water and soprevent the type of emulsion due to these metallic soaps. Suchproposals, however, have been limited to the use of alkaline reagentssuch as the alkali metal carbonates and silicates and neutral salts suchas the alkali metal sulfates and, by reason of the low order ofeffectiveness of these materials, such treatments have not givensatisfactory results nor come into practical use.

We have discovered that the various alkali metal phosphates are moresuitable for this purpose than the salts heretofore used, and that thedisodium phosphate (Nail-IP04) is particularly efllcacious. We have alsodiscovered that the eiliciency of the phosphate in preventing" theformation of tight emulsions is greatly increased by thesimultaneousaddition to the well of a free acid, preferably sulfuric acid, inquantity sufllcient to bring the water produced with the oil to a pHwithin the range. pH 6.5 to pH 7.4. Within this range the sulfuric acidprecipitates any barium present in the water as the very in-.

soluble sulfate, while the phosphate salt pre-- ci'pitates the calcium,magnesium, iron, and aluminum in a fiocculen-t gelatinous form.

In the practical application of the invention a stream. The rate ofintroduction is so regulated, and the composition of the stream soadlusted, that the quantity of acid so added will b11118 the pI-Iof theproduced water to a value as close to 7.0 as possible, and within therange pH 6.5 to pH 7.4, and that the quantity of the phosphate issuflicient substantially to precipitate the soap-forming alkali earthsand heavy metals. This latter quantity may be predetermined in apreliminary titration of the water with a standardized phosphatesolution, or it may be controlled while feeding the solution byobserving the condition of the oil-water mixture produced by the well.when using sodium diphosphate the quantity required may be from 1 partsalt to 1000 parts water upwardly, according to the initial hardness ofthe water.

The product from the well during this treatment may consist of freewater and relatively water-free oil, or the water may be suspended inthe oil and lightly emulsified. In the latter case it will be found thatthe emulsion is not refractory and that it will break and permit thewater to be separated by simple settling at a temperature at which theoil is fully liquid.

I It will be found that the oil resulting from this settling or otherphysical method of separating the oily from the aqueous phase will besubstantially free from calcium and magnesium chlorides, the admixtureof the treated waterwith the oil in the pump and thedelivery tubingbeing ordinarily sufficient to bring the solution into contact with thesuspended particles and thus precipitate these metals as phosphates.

The same treatment may be applied to the removal of these corrosivechlorides from crude oils to be refined by distillation. In thistreatment the oil is agitated and emulsified with a dilute aqueoussolution of an alkali metal phosphate, preferably disodium phosphate,previously adjusted to about pH 6.5 by the addition of sulfuric acid.The thus produced emulsion is then settled and it will be found that thesupernatant oil is substantially free from the chlorides of calcium andmagnesium which unless removed are highly corrosive to refinerydistillation and condensing equipment.

We claim as our invention: a

1. In a method of treating an oil well normally producing hard wateralong with the, oil which includes introducing into said well a streamoi an aqueous solution, the improvement which coniprises: using asolution of an alkali metal ph sphate acidulated with a mineral acid ass id introduced stream; and so controlling the composition and volume ofsaid introduced stream as to bring the water produced from said well toa pH value within the range from 6.5 to 7.4 and to precipitate at leasta portion of the alkali earth metal and heavy metal constituents of saidwater as gelatinous phosphates.

2. A method substantially as and for the puraaomoa pose set forth inclaim 1 in which said alkalimetal phosphate is disodium phosphate.

3. A method substantially as and for the purpose set forth in claim 1 inwhich said mineral acid is sulfuric acid.

4. The method 0! freeing crude petroleum from calcium and magnesiumcompounds which comprises admixing said petroleum with an aqueoussolution of an alkalimetal phosphate acidulateol with a mineral acid,the composition and quan- 10' tity of said aqueous solution being soregulated 01' said calcium and magnesium compounds as phosphates, andphysically separating the aqua ous from the oily phase after saidadmixture.

